The present invention relates to a cooling fan, in particular to a radiator fan for motor vehicles with an electronically commutated electric motor.
Because of the aerodynamic optimization (C-values), fan wheels with specific diameters are required for cooling internal combustion engines. This restriction also applies to condenser fans which are arranged in front of the actual radiator and condenser of the air-conditioning unit. There is therefore a demand for compact electric fans with a short length, for which a speed adjustment is also desirable for reasons of noise and performance. For this, a conventional electric motor with brushes and an electronic combinational circuit module is particularly suitable or even a brushless motor with corresponding power electronics.
To minimize interference, the electronics must be located as close as possible to the motor because the short cables radiate less interference energy. But, on the other hand, direct heat transfer from the motor to the electronics must be avoided. For this purpose, according to U.S. Pat. No. 4,668,898 the electronics are arranged in their own control casing which is connected to the motor casing by struts. This electronically commutated motor is not suitable for a compact fan for cooling internal combustion engines.
Furthermore, an electric motor with an external rotor and a fan wheel connected to it is known from German Patent Laying-Open Document 38 20 857, in which the electric motor is designed as a direct-current motor with electronic commutation. In this case, the electronic components are arranged on a printed circuit board, which is attached to a fan casing which has cooling fins. This electronically controlled direct-current motor cannot be used for cooling condensers and/or radiators in motor vehicles.
An electronically controlled electric motor with a fan wheel for sucking in cold air is also known from German Patent Laying-Open Document 44 18 000 A1, in which the drive electronics are axially continued in a control casing which has cooling fins arranged at least on its external peripheral surface in the direction of flow of the cold air flow produced by the fan wheel. This motor certainly has a compact design, but its axial extension prevents easy mounting because of the very limited space available between the radiator and the engine in a motor vehicle.
Finally, a radiator fan for motor vehicles with an electronically commutated electric motor is known from German Patent Laying-Open Document 196 12 679 A1, in which the drive electronics are arranged in a control casing which is connected to the radiator casing. This control casing is attached to the radiator casing outside the outer ring of the fan wheel and has cooling fins which project as far as the center of the cold air flow.
The object of the invention is to further develop a cooling fan, in particular a radiator fan for motor vehicles, in such a manner that an even better cooling of the electronics in the electronics casing is achieved.
The above object has been achieved according to the invention in a cooling fan, in particular a radiator fan for motor vehicles, arranged in a radiator casing with an electronically commutated electric motor, a fan wheel or impeller driven by its rotor, and electronics influencing the speed and/or output of the electric motor, which are arranged in an electronics casing attached to the radiator casing radially outside the impeller. The outer surface of the electronics casing has cooling fins, the free ends of which project into the cold air flow produced by the impeller. According to the invention, the free ends of the cooling fins projecting into the cold air flow have air diverting elements, through which a part of the predominantly axial cold air flow produced by the impeller is diverted in a radial direction relative to the impeller and then in a longitudinal direction of and toward the other ends of the cooling fins arranged on the surface of the electronics casing.
The cooling fan according to the invention is characterized by an improved cooling effect of the electronics casing, for which only simple additional tools and/or slight constructional changes are required in comparison to the known fans.
In an advantageous embodiment of the invention, the air diverting elements comprise an air-guiding sheet-metal plate that covers the free ends and the back edges of the cooling fins so as to close the back of hollow spaces between adjacent ones of the cooling fins. This achieves a simple diversion of a part of the axial cold air flow by means of a simple baffle plate. This in turn ensures that the cold air sweeps over the whole length of the cooling fins.
According to a further embodiment of the invention, the free ends of the cooling fins projecting into the cold air flow are shaped to extend counter to the rotational direction of the impeller in such a manner that the tangential air flow produced by the impeller is diverted radially outward. This guarantees a sure diversion of part of the cold air flow produced in the rotational direction of the fan wheel by means of the special shape of the free ends of the cooling fins.